One of the most significant metrics for space propulsion systems is specific impulse, which is the ratio of thrust produced to the rate of propellant consumed. Specific impulse has units of seconds, and is essentially the number of seconds that a pound of propellant will produce a pound of thrust. The higher the specific impulse the less propellant mass and associated tankage required for a given space mission. The Stafford Synthesis Group (Stafford, America at the Threshold) concluded that future space exploration will require advanced propulsion technologies. Subsequently, NASA conducted the Breakthrough Propulsion Physics Program (NASA/TM-1998-208400), one of the three main goals of which was to “discover new propulsion methods that eliminate or dramatically reduce the need for propellant. This implies discovering fundamentally new ways to create motion, presumably by manipulating inertia, gravity, or by any other interactions between matter, fields, and spacetime.” Therefore, an electromagnetic spacecraft propulsion system such as the present invention, that does not require expendable propellant and thus has an effectively infinite specific impulse, would address these needs and greatly reduce the cost of doing business in space.
Sir Isaac Newton's well-known Third Law of Motion, which states “To every action there is always an opposed equal reaction; or, the mutual actions of two bodies upon each other are always equal and directed to contrary parts”, has been interpreted as all-encompassing for over three hundred years. The Newtonian interpretation excluded the possibility of “reactionless propulsion” of a solid body. However, the discovery of electricity and magnetism, the new branch of electrodynamics resulting from Maxwell's Equations, and the subsequent rise of relativistic electrodynamics and quantum electrodynamics, led to a new interpretation of the famous “Third Law of Motion”.
One of the important characteristics of an electromagnetic (EM) wave is that it can transport energy from point to point. The rate of energy flow per unit area in a plane electromagnetic wave is described by the Poynting Vector S, defined as the cross-product of the instantaneous E-field and B-field comprising the EM wave. The direction of S gives the direction in which the energy moves. (Resnik and Halliday, Physics Parts I and II). Less familiar is the fact that EM waves also transport linear momentum. Just as Poincare noted in 1900, Stebens explains that the electromagnetic field closely resembles a relativistic fluid, composed of quantum particles (photons), which transmits properties and responds to forces in much the same way as an Eulerian fluid (Stebens, Forces on Fields). In electromagnetism, as in Newton's solid body mechanics, the force on matter from the electromagnetic field is balanced by an equal and opposite force from matter on the field. Stebens presents an excellent proof which can be derived from Maxwell's equations and the Lorentz force law. The proof relates the reaction momentum change of the electromagnetic field to the time rate of change of the Poynting Vector, the divergence of the Maxwell Stress Tensor, and Einstein's relativistic mass-energy relation (Forces and Fields, op.cit.). Straightforward application of the Biot-Savart Law from classical physics shows that the magnetic field from a rectangular conducting coil acting on an isolated current segment generates a unidirectional force on the coil-segment system. By recognizing that electromagnetic fields can transport both energy and momentum, apparent “violations” of the Third Law are mathematically resolved by including modern field transport physics in the analysis of the reaction process.
Field propulsion, which employs electromagnetic field effects for generating propulsion forces, expels no reaction mass, and therefore effectively has an infinite specific impulse. As is well known to anyone skilled in the art, a moving charged particle generates a magnetic field. It is also well known that a magnetic field generates a force on a moving charged particle, namely the magnetic component of the full Lorentz Force, which component is proportional to the vector cross-product of the particle velocity vector and the magnetic field vector at the particle location. A common example is the well-known mutual equal-and-opposite forces on parallel conductors, which may be calculated by anyone skilled in the art through the use of the Biot-Savart Law. Prior to modern electrodynamics, the required compliance with Newton's Third Law (NTL), it has previously been accepted that the aforementioned magnetic interactions could not be used to produce a propellantless propulsion system. As discussed above, modern electrodynamics has shown that this is no longer a valid assumption.
Physicists have known since at least 1952 that apparent violations of NTL, in cases where force interactions involve charged particles and electromagnetic fields, simply do not account for the momentum carried in the fields themselves. As noted by Cullwick over sixty years ago: “The following simple relations between electromagnetic momentum, the Poynting vector for energy transport, and mass-energy equivalence do not appear to have received general recognition in connection with the validity of Newton's Third Law when applied to electromagnetic forces (Cullwick, Nature).” Since then, over thirty US patents and at least two dozen foreign patents have been issued for propellantless propulsion devices. Most importantly, recent experimental investigations conducted by NASA with an EM drive device (White, AIAA Journal of Propulsion and Power) have definitively confirmed that EM field propulsion is a reality.
Nobel Laureate Richard Feynman (The Feynman Lectures on Physics), among others, noted that the magnetic interaction between two charged particles moving orthogonally to each other apparently does not satisfy NTL in classical Newtonian dynamics. But, as Feynman explains (Lectures, op.cit.), if the changing momentum of the electromagnetic fields of the two particles is included, then overall momentum is conserved. Engineering exploitation of this situation, to date, has not been effected due to the “circuit completion” problem. While isolated moving charges may apparently violate NTL, when they are confined as part of a complete closed circuit, then by application of Gauss' Law the net forces on each circuit are found to be equal and opposite in accordance with NTL.